The present invention more particularly relates to a vertical pump assembly for high pressure cleaners with wobble plate, advantageously connectable to an internal combustion engine the shaft whereof sets said plate in rotation; a pump assembly of this type is described, for example, in U.S. Pat. No. 5,494,414.
It is known that high pressure washing equipment, known by the term “high pressure cleaners”, has long been used for cleaning work, especially of large surfaces.
This equipment is made according to various types for industrial, professional or hobby use and comprises a motor-pump assembly that pressurises the fluid, typically water with detergents, fed through an inlet conduit. Water under pressure comes out of an opposite conduit whereto a hose is connected; the latter is associated to a dispenser that may be actuated manually, which comprises a nozzle wherefrom water can come out with a more or less concentrated jet. Two or more dispensing nozzles are generally provided, to be used alternatively according to the needs. In this washing equipment, the wobble plate that moves the axial pistons is coupled to the motor shaft, generally an electrical motor. According to a traditional embodiment, the pistons are seated and guided in the axial sliding into a housing that is fixed to the body wherein the free end of the motor shaft protrudes; the wobble plate is keyed on the latter. Said body that seats the free end of the motor shaft at the bottom forms a connection flange to the motor, and as for the housing, it is generally made of aluminium or alloys thereof.
Both the housing and the body that seats the motor shaft end substantially have the same diameter and are connected to each other by screws, arranged along the periphery of the housing itself. The pump head develops above the latter, with the fluid conduits and the relative valves.
It has been noted that this traditional solution has a considerable drawback.
In particular, the housing is subject to very high working pressures in the central zone, which is significantly far from the peripheral parts wherein the connecting screws to the underlying body are arranged. A pressure level equal to about 2600 PSI is allowed in the presence of a mean thickness of the housing comprised between 3.0 and 5.0 mm referred to the central zone thereof. As a consequence, an increase of fluid pressure even as little as 5% may lead to dangerous effects due to the yielding of said housing. An increase in the working pressure should therefore be correlated to an increase in the housing thickness, especially in the central zone, but this would lead to an increase of both the overall weight and the production costs.